Fixed #2445 -- Allowed limit_choices_to attribute to be a callable.

ForeignKey or ManyToManyField attribute ``limit_choices_to`` can now
be a callable that returns either a ``Q`` object or a dict.

Thanks michael at actrix.gen.nz for the original suggestion.

tests/model_forms/models.py

@@ -8,6 +8,7 @@ words, most of these tests should be rewritten.
 """
 from __future__ import unicode_literals
 
+import datetime
 import os
 import tempfile
 
@@ -71,7 +72,6 @@ class Article(models.Model):
     status = models.PositiveIntegerField(choices=ARTICLE_STATUS, blank=True, null=True)
 
     def save(self):
-        import datetime
         if not self.id:
             self.created = datetime.date.today()
         return super(Article, self).save()
@@ -329,3 +329,21 @@ class CustomErrorMessage(models.Model):
     def clean(self):
         if self.name1 == 'FORBIDDEN_VALUE':
             raise ValidationError({'name1': [ValidationError('Model.clean() error messages.')]})
+
+
+def today_callable_dict():
+    return {"last_action__gte": datetime.datetime.today()}
+
+
+def today_callable_q():
+    return models.Q(last_action__gte=datetime.datetime.today())
+
+
+class Character(models.Model):
+    username = models.CharField(max_length=100)
+    last_action = models.DateTimeField()
+
+
+class StumpJoke(models.Model):
+    most_recently_fooled = models.ForeignKey(Character, limit_choices_to=today_callable_dict, related_name="+")
+    has_fooled_today = models.ManyToManyField(Character, limit_choices_to=today_callable_q, related_name="+")

tests/model_forms/tests.py

@@ -22,7 +22,8 @@ from .models import (Article, ArticleStatus, BetterWriter, BigInt, Book,
     DerivedPost, ExplicitPK, FlexibleDatePost, ImprovedArticle,
     ImprovedArticleWithParentLink, Inventory, Post, Price,
     Product, TextFile, Writer, WriterProfile, Colour, ColourfulItem,
-    ArticleStatusNote, DateTimePost, CustomErrorMessage, test_images)
+    ArticleStatusNote, DateTimePost, CustomErrorMessage, test_images,
+    StumpJoke, Character)
 
 if test_images:
     from .models import ImageFile, OptionalImageFile
@@ -521,6 +522,12 @@ class FieldOverridesTroughFormMetaForm(forms.ModelForm):
         }
 
 
+class StumpJokeForm(forms.ModelForm):
+    class Meta:
+        model = StumpJoke
+        fields = '__all__'
+
+
 class TestFieldOverridesTroughFormMeta(TestCase):
     def test_widget_overrides(self):
         form = FieldOverridesTroughFormMetaForm()
@@ -1921,3 +1928,34 @@ class ModelFormInheritanceTests(TestCase):
         self.assertEqual(list(type(str('NewForm'), (ModelForm, Mixin, Form), {})().fields.keys()), ['name'])
         self.assertEqual(list(type(str('NewForm'), (ModelForm, Form, Mixin), {})().fields.keys()), ['name', 'age'])
         self.assertEqual(list(type(str('NewForm'), (ModelForm, Form), {'age': None})().fields.keys()), ['name'])
+
+
+class LimitChoicesToTest(TestCase):
+    """
+    Tests the functionality of ``limit_choices_to``.
+    """
+    def setUp(self):
+        self.threepwood = Character.objects.create(
+            username='threepwood',
+            last_action=datetime.datetime.today() + datetime.timedelta(days=1),
+        )
+        self.marley = Character.objects.create(
+            username='marley',
+            last_action=datetime.datetime.today() - datetime.timedelta(days=1),
+        )
+
+    def test_limit_choices_to_callable_for_fk_rel(self):
+        """
+        A ForeignKey relation can use ``limit_choices_to`` as a callable, re #2554.
+        """
+        stumpjokeform = StumpJokeForm()
+        self.assertIn(self.threepwood, stumpjokeform.fields['most_recently_fooled'].queryset)
+        self.assertNotIn(self.marley, stumpjokeform.fields['most_recently_fooled'].queryset)
+
+    def test_limit_choices_to_callable_for_m2m_rel(self):
+        """
+        A ManyToMany relation can use ``limit_choices_to`` as a callable, re #2554.
+        """
+        stumpjokeform = StumpJokeForm()
+        self.assertIn(self.threepwood, stumpjokeform.fields['has_fooled_today'].queryset)
+        self.assertNotIn(self.marley, stumpjokeform.fields['has_fooled_today'].queryset)